454 died, now it sounds like it's eating itself!

A blown head gasket will suck water from the water jacket right pass the defect in the head gasket.

Going over your comp readings again, you should just do a complete rebuild. You'll need a valve job anyway and unless you want to measure each valve lift for cam lobe wear, just get a new cam and lifters. More than likely you have cast hypereutectic pistons. You don't need forged.

I'd be a little leary of engine kits unless they're marine kits. At the very least you should get all the cam specs and compare them to marine.

Oh, forgot to ask if you have twins. Too much difference in power between engines can run into problems. Just a valve job might do it.
 
Hi everyone;

So after a lot of shopping around (and quite a few conversations with various machine shops around the country), we've decided to replace all 8 pistons with the newer design, rather than just replacing the one bad one. The new ones are still cast, but evidently the ring groove is wider (so different rings as well), and the spacing might be slightly different too. (J-D, this could be in reference to the condition you were talking about; I couldn't get a straight answer as to why the changes were made by GM, however.)

We found an outfit out of Texas (who also sells on E-bay) that was willing to make us a custom marine rebuild kit with all the parts we wanted for a reasonable price. Still waiting for the stuff to arrive, but once the parts get here it should be a slam-dunk to install everything. Oh yeah, and just to be safe we also decided to order all new head and exhaust manifold bolts...

Gregory - our experience mirrors yours. Most machine shops said the same thing: swap all 8 pistons. It's cheaper, and in the long run it's safer from an engine balance standpoint. Also, the new pistons are supposed to be superior anyway (due to the changes with the rings), so that's a plus. I guess the proof will be when we put it in the water!

Charlie: This is a single engine boat. (Bravo 3) As for water from the blown head gasket, we wondered about that as well. However, we inspected the gasket, the head, and the cylinder block very carefully, and the gasket is completely intact around all the water passages. So if water got in there, it almost had to come through the valves. (You can see this in the pictures I posted above.)

Another interesting thing is that only the #5 cylinder has any sign of water ingestion, which is very odd. At the very least, you'd think that some water would have been pushed over into the adjacent cylinder through the gap in the head gasket between the two cylinders. Then too, if the water came up from the exhaust (flappers were completely gone, remember), then it's strange that it only got into the # 5 cylinder and not the others.

I don't know. Maybe chasing the water is a red herring. The consensus from everyone I've shown the broken piston to is that the engine cross-fired and blew the piston and the head gasket at roughly the same time. But the clean, shiny metal on the # 5 piston crown still has me wondering about water...

But regardless of the source, we are eliminating all possible future instance of water ingestion. New manifolds, new flappers, and of course new gaskets on the head. Plus they will deck the heads before we put them on. (Should be about finished with the work on the head by now - we are expecting a call any day now.) The machine shop hasn't called us with any problems so far, so that's encouraging. (Estimated turn-around time was 1 week, which will be tomorrow.)

I'll post again once we have all the parts in hand to begin re-assembly. And thanks to everyone for chiming in on this thread!

Adam
 
There was a lot of discussion several years ago about some boat designs not having enough rise in the exhaust. In your case though the missing flappers are a possible cause.
 
Be sure to also deck the gasket mating surfaces of the manifold and riser, and of any riser adapter if you have room to add one to increase height above waterline.
When purchased , they look flat but are not , as is easily seen if one uses a black marker to cover that surface and begins to deck with a sharp flat mill file.
And I suggest retorquing all fasteners to spec after a few running heat cycles.

More power to you. At this point I would be springing for a shin new reliable engine, but my hat is off to you for diving into this educational rebuild project together with your son. There will be great memories.
 
What size engine is it you're building? Most of my engine building has been SBC(Small Block Chevy) and my last 3 or 4 builds have been the 400ci smallblock. They have power comparable to the big block but with small block prices. You should consider building your own engine one of these days. Lots of math and you learn a lot about engines.
 
hey Charlie in these days do you have to measure ring gap, piston and skirt clearance or are parts made with close tolerances so that you can just bolt everything together?
 
Hey folks! Sorry for the long break... Been waiting for parts and only just got a chance to work on the engine last Friday. Unfortunately, things didn't go quite as planned. (Of course!)

I cleaned up the block and ran a tap through all the holes for the head bolts earlier, and I honed the cylinder walls too. So on Friday when the new pistons arrived we started by pressing out the old wrist pins to free the connecting rods. This ended up being a lot more difficult than I thought, even with a heavy-duty hydraulic press. Took us a good 2 hours of fiddling to get it done. (Ever try to balance a round piston with a heavy connecting rod hanging off it on a flat table? Yeah, not fun.) Ended up using all sorts of scrap steel pieces as cribbing to form a makeshift jig to hold everything, and even then it was tedious. But we got all the rods free.

Then we tried installing the rods on the new pistons using the shiny new wrist pins that came with the new pistons. Except they wouldn't fit! We tried everything we could, but they were just too tight. I started to worry that we might bend the piston skirt. (Couldn't even get them to go through the hole in the piston, let alone through the hole in the connecting rod.) Then I got the bright idea to try one of the old wrist pins..

Well, long story short, we were able to get one of the old wrist pins to press in. We lubed it up with oil and had to use a good bit of force from the press, but we got it completely installed. But then when we removed it from the press, we were horrified to see that the rod would not move in any direction! It was seized on the pin, and the pin was seized on the piston. Crap - now what?

At this point, I figured we needed some expert advice, so I called the local machine shop that reworked the heads for us. And they said to just bring the stuff down to them and they would mount the old rods on the new pistons for like 60 bucks. No problem! Money well spent! So we headed to the shop.

When we got there, the guy took one look at what we had done and started shaking his head. Evidently you can't just press the new wrist pins into place. (Or at least, not for a big-block.) He said you have to cool the wrist pin (in a freezer) and heat the rod up to red-heat with a torch. Then you have about 30 seconds to drop the pin in place. When the rod cools, it is supposed to seize on the pin, and the entire pin should roll freely (and slide side to side slightly) in the piston. Also, you are never supposed to oil the pin until after it's installed, because the oil actually makes it harder to get the pin installed.

The bad news is that by using the press to force the old rod onto that one piston, I actually galled the metal around the hole in the skirt a little bit, and I also bent the piston skirt slightly due to the extreme pressure from the hydraulic press. But fortunately the damage was very slight. Just enough to make one hole in the skirt not quite perfectly round anymore. So they honed out the hole slightly and then they were able to get the pin to go in. It fits tight with no play, so we should be golden there.

However, while we were talking about all this with the guy at the machine shop, he asked me how I knew which rod went with which cylinder, since he couldn't find any markings. That's when I realized I had made a major mistake... I labeled all the rod caps, but in my haste to disassemble the engine earlier last month I forgot to label the rods! D'oh! Fortunately, the guy at the shop agreed to mic them and re-match them for me. (True, I could have done this myself, but at that point I wanted to be sure it would be right, so I figured it would be best to let an expert do it.) I gave him the rod caps and nuts, and the next day everything was put together and numbered. Whew!

So now we are ready to re-assemble the engine. Unfortunately, it will have to wait until my schedule lines up with my son's schedule, so it might be another week or two. Sandy, regarding waterline clearance, we did measure that before we pulled the motor, and it looks like the top of the elbow is at least 14 inches above the waterline, if not higher. I'll try to take a more accurate measurement when we put it back in the water. Charlie, yeah - this is a big block (454). It's only the second engine I've torn down, and I'm still learning, but you're right - it's not as difficult as some people would have you believe. There are a few "gotchas" to watch out for, but even so I'd definitely do it all again if I had to. And Bruce, regarding piston ring gap and skirt clearance, everyone I've spoken to says that these days it's all standardized and you don't need to worry. (Although you still need to stagger the gaps on the rings, of course.)

Hopefully the next update will be one where the engine is back in the boat! Take care all...

Adam
 
One thing I do as a matter of course is measure cylinder for straight and true. Oil cylinders. Get a ring and put it in a cylinder 90* and turn. use a piston to true ring to cylinder...push ring down with piston slightly will square the ring to the cylinder. Measure ring gap. Push ring down another inch or so and measure ring gap. Do it again til you have readings of the complete cylinder. Hopefully all readings are the same. That means the walls are straight and true.

Also, the head gasket didn't look marine(SS).
 
Hey Charlie;

Since the cylinder walls didn't show any signs of damage (no scoring at all), we didn't bother checking the cylinders to ensure they were straight and true. I did mic a couple of them just to be sure they were within tolerance, but nothing beyond that. (Just wanted to be sure standard rings would still be sufficient.)

As for the gasket, it did look a bit strange, but it also peeled a bit when we pulled the head off, so that might explain it. The thing that struck me as odd was the funny way the holes for the cylinders were "bent" aft, almost like the head had been over-torqued and this somehow forced the metal ring that surrounds each cylinder to shift to bow out to the rear a little bit. But the new gaskets look exactly the same way, so this must be a design issue. (New gaskets are Sierra-branded marine head gaskets, so I know they are right.)

Anyway, we did work on the engine some more, first on Friday and again yesterday. Friday didn't start out too well... We got all the pistons in, but as we were torquing down the rod caps we snapped one of the rod bolts! (D'oh!) Fortunately a local shop had a fastener kit for the 454 in stock. But I had to buy all 16 bolts and nuts, which set me back $90. (I figure I was the one with the torque wrench in my hand when it snapped, so I had to buy the new bolt.)

Once we got the bottom end put back together, we started on the heads, and that went a lot easier. By the end of the day on Friday both heads were on and torqued. So yesterday we put the intake on, and then bolted the new exhaust manifolds on. But of course, it couldn't go perfectly smooth... We broke one of the plastic water fittings that feed water to the exhaust manifold. (Trying to remove it from the old manifold and it just snapped!) Looking around for a local source to replace that fitting right now.

Still, we're in pretty good shape. If all goes well, on Tuesday we plan to put the engine back in the boat. Then we've got a lot of work to do re-installing all the bolt-on stuff (alternator, power steering pump, mercathode, etc). With any luck though, by Wednesday we should be able to at least fire up the engine while it's sitting on the trailer. If that goes well, then next week we might put her in the water. (Crosses fingers)

I'll be sure to post again later this week. Really hope we don't run into any more snags... We are very close now, but there are still plenty of ways we can screw up, so we'll take our time.

Adam
 
some bolts are intended for single use, Don't know if that applies to rod end bolts.
 
Definition: experienced mechanic

One who has already broken the one thing that you should not break.

--------

There are many experienced mechanics here. :) Hopefully they will be able to save you time and money. Enjoy the rebuild!
 
OK, so we did some more work on the engine this week. Got the manifolds on, got it re-installed in the boat, and hooked up just about everything in the engine compartment. Still don't have fuel, plugs, plug wires, belts, or the outdrive connected yet, but we did put the oil in the engine and roll it over on the starter. After it primed up, we were pleased to find we had 40 PSI of oil pressure! So that made us feel really good.

Getting that big engine back into the boat was quite the challenge. It's a lot taller when it's fully dressed out! (When we pulled it, we had already stripped the manifolds and heads off, so it was much shorter and lighter.)

We had a tall traveling A-frame that straddled the boat, but even with the hoist all the way up the engine wouldn't fit over the transom, so we had to open the transom door and bring it through there. Then we couldn't get the engine hatch open, so we had to take the Bimini top off so we could move the whole A-frame (with the engine still dangling below) forward enough so it would clear the hatch. The engine was right behind the captain's seat when we finally got the hatch open!

Then we slid the frame back and used the trolley to move the engine back into the centerline. And with a little elbow grease and the proper application of more than a few 4-letter words, we were able to coax the beast back down into the engine compartment. :) Broke a couple hose clamps installing the exhaust elbows, flappers, and associated plumbing, but that wasn't a big problem.

Tomorrow we plan to do a compression test, and then hook everything else up and try to start it up on the flush muffs. Then we need to check the ignition timing to be sure it's accurate. If all goes well, we will put it in the water next week Thursday for it's first sea trial. (Crossing fingers!)

Adam
 
Too bad so many ROs live so far away. I made a mobile crane because I was pulling boat engines often enuff to justify the effort. It's on a 2 wheel trailer which makes very maneuverable. it raises 10 ft with a 7 ft reach.

About your engine, does it have a roller cam or flat tappet cam. Flat tappet cam requires a special cam break-in procedure. Roller cams don't need a break-in.
 
Charlie;

We actually had access to a very nice traveling A-frame that was just over 12 ft tall. It's just that my son's boat sits very high on the trailer and has a *LOT* of freeboard. Still, with a little extra work we were able to make it work. Oh, and this engine is flat tappet. (The generation after his had the roller cam.) Although for this rebuild we didn't replace the cam or the lifters, so that's not a huge concern.

Even so, we plan to baby it during the break-in period. (Do not exceed 3/4 throttle, do not exceed 4000 RPM, avoid prolonged idling, avoid running at any fixed speed for more than 5 min, avoid rapid acceleration, and so on...) The next 15 hours of boating is going to be a bit restrictive, but it's what needs to be done to ensure long life on the engine.

Had lots of little issues earlier in the week, including completely WIPING the sea water impeller because while we had it idling on the flush muffs (to set the ignition timing), the damned flush muffs fell off, and we didn't notice! So, yeah, we ruined that poor pump. Fortunately the temp never got above 190 before we shut it down.

Got the replacement parts installed yesterday, and also plugged a couple drain holes in the new exhaust manifolds that were not present on the old ones. (You'd think new manifolds would come with plugs, but nooooo.) Then we replaced some old fuel line clamps (leaks - ugh). We also did some maintenance on the trailer, and generally cleaned things up a bit. So we were finally able to put the boat in the water today.

As for the sea trial itself, I'd say it went "OK". Initially it was great - no issues at all. Engine very smooth, temp rock solid stable, and 60 PSI of oil pressure. Put it on plane after about 5 min and started varying the speed up and down from 2500-3500 RPM. Ran it for nearly an hour. But then we had a couple hiccups.

First, we noticed the battery voltage needle was jittery. Reading around 13.5 volts or so, but it would jerk down to around 12.5 and then back up to normal every few seconds. It actually had been doing this all along, but we didn't think it was important until the entire ignition system cut out for a split second while we were cruising. Just a sudden loss of power for about a half second, then right back to normal like nothing had happened. It did this maybe 3 or 4 times.

We throttled down to a slow plow (maybe 2000 RPM), and I noticed that the oil pressure had dropped off to around 45 PSI. Hmmm. It was at 60 PSI earlier. We were only a few miles from the landing, so we headed towards the dock. I thought the engine sounded funny, so I throttled down to idle and then slowly back up to planing speed (2500 rpm), and the engine definitely seemed to be loping a bit. But then it smoothed out and ran fine all the way to the dock.

We figured we shouldn't push our luck, so we put it back on the trailer. I did notice that the oil pressure dropped down to like 25 PSI when we were in gear at just above idle, which bothered me. We used to have more pressure than that just rolling the engine over on the starter!

Once we got it on the trailer and shut down I went over everything. I couldn't see anything amiss though. I checked the dipstick, and the oil is fine. No sign of water, no sign of metal flakes, and the level is right where it should be. No discoloration at all. All the distributor wiring looks fine, and the hold-down bolt is plenty tight. I did notice that the alternator belt is a bit loose, but I don't think it was bad enough to cause the strange voltage readings we saw. (If the belt slipped, we should have heard it...)

Anyway, after reading some other threads about ignition issues, I'm starting to suspect the sensor mounted on the distributor and/or the ignition coil itself being bad. Tomorrow I'm going to check with the local Merc dealer and see if they have the parts in stock. Cheap insurance, I think... (Given that we're pretty sure it was an ignition issue - specifically a crossfire - that cause the damage that forced us to rebuild the motor, I want to make sure we don't have more ignition problems!)

I also want to do another compression test before we put it back in the water. I did one last weekend before we started it for the first time, and we were 120 PSI (+/- 5) on all cylinders. I want to be sure we're still in that range. That drop in oil pressure has me spooked.

And yes, I know it's more than likely just a sensor going bad. 60 PSI of oil pressure is insanely high anyway, so the fact that it dropped to 45 on plane (and 25 at idle) probably means it's just reading normal now. But I want to be sure it's not a sign that something else is about to break! (Guess I need to check to see if they have an oil sending unit in stock too...)

If I can get those ignition components locally and get them installed, we will probably put it back in the water either tomorrow or Saturday. And if we see any more issues with the engine sounding/performing strangely, I might just drop the oil out after 3-4 hours just to make *SURE* we don't have any metal in the pan. (After all, oil is cheap compared to engine parts!)

I'll update again after this weekend.

Adam
 
OK, so we put some more hours on the engine over the weekend. (Up to around 5 hrs total run time since the rebuild now.) We also replaced the sensor in the distributor and put a new coil on just for good measure. But even with all that, we've still got a small problem.

The engine starts and runs fine up to about 3000 RPM. But it won't go much past 3000 (under load, that is) no matter what we do. I'm pretty sure it's a carburetor issue, so that's where we plan to start. Thinking it could be a clogged jet, or maybe a clog in the screen filter where the fuel line hooks up to the carb. It sucks to be this close and still be having problems... (Grrr!)

The oil pressure issue mentioned earlier seems to be a non-issue. Evidently, 25-40 is normal, and 60 is expected when it's cold or at higher RPMs. So that's fine. Just need to figure out why it's bogging when we try to throttle up.

Adam
 
What were your WOT RPMs before the rebuild (assuming no prop changes made)?
 
Does it still run smoothly at 3000 WOT?
Any chance the throttle adjustment , cable jacket clamp has slipped?
Does the linkage pull open the carb secondaries when it should?

A good vac gauge test can reveal or rule out a lot of possibilities very quickly, as demonstrated when you click on the green links here:
http://www.secondchancegarage.com/public/186.cfm
 
Yeah, anything in particular with the carb makes you think that's the problem? I would have guessed the ECM if TBIV ign. Had that problem.

Back to the carb. Q-jet? The secondaries can be adjusted too loose so that the secondary plates open too soon and too much. You can actually close the secondaries completely while running and, depending on speed(RPM), will run fine. It's the secondaries opening too soo or too much that causes lean or excessive lean condition. It will make a loud sucking sound and may start poping out the carb. Will limit rpm unless you can get it over the 'hump'.
 
Gregory: Previous RPM at WOT was 4600. When we first put the boat in the water after the rebuild we intentionally avoided WOT because we wanted to gently break-in the rings and new rod bearings. However, we did rev it up to 3500 several times for short periods, and we always kept it above 1500 RPM to maintain adequate cylinder pressure. But near the end of that first sea trial we noticed that it bogged down on us (at around 3000 RPM), at which point we slowed down and headed straight for the dock. At the time, I was thinking ignition components, especially since we definitely had a few total ignition cut-outs during that first run. That's why we changed the coil and the sensor in the distributor. But after we put it back in the water, we noticed that we couldn't rev up past 3000.

Sandy: Yes, it runs very smooth at 3000. As you throttle up past that point, the RPMs don't change but you can hear the engine note change as it begins to bog. That's what leads me to believe it's starving for fuel. We didn't do anything to the carb during the rebuild (we actually left it attached to the intake), but it was turned upside-down to drain the fuel. (I know, I know - stupid move...) I'm thinking that the dirt/varnish/crap at the bottom of the bowl from 20 years of running probably splashed all over the inside of the bowl, and after we put it back together and ran it, at some point some of that re-distributed trash made its way into one of the jets. However, it could also be nothing more than a loose/broken linkage. I need to verify that the secondaries are free and moving, and I also need to check the throttle cable. But assuming those are OK, it's just about got to be the jets.

As for checking vacuum, I honestly hadn't considered that. This engine has the Thunderbolt V ignition, so the timing advance is all electronic, and there aren't any vacuum hoses on the engine anywhere. But I could hook a vacuum gauge directly to the port on the carb and see what's going on... I still have a vacuum gauge in the toolbox somewhere. I think I'll bring it along next time we work on it.

Charlie: As above, the carb was inverted, and while these days that isn't usually a big deal (not compared with the carbs of old!), it can still shake up all the settled gunk in the bottom of the bowl. That's my working theory anyway. (Although as Sandy mentioned, it's also possible the linkage to the secondaries has fallen loose. I plan to check that first before we pull the carb.) As for ignition issues, I've been told the Thunderbolt V is far more reliable than the Thunderbolt IV. Also, all other ignition components have now been replaced.

The carb is actually a 750 CFM Webber. Evidently Merc moved away from the venerable Quadra-jet back in the 90's in favor of the Webber. Not really sure why, but these Webber carbs seem to be pretty bullet-proof. I had the 600 CFM Webber on my old '95 Bayliner (4.3L Merc), and I never did anything to it in the 10 years I owned the boat!

While we were running I was already thinking about the possibility that it might be fuel related. I knew that low fuel would result in a lean-burn condition, so I was listening for sucking or a pop through the carb, but I never heard it. Then again, I've only ever heard engines pop like that when accelerating suddenly from near-idle with a damaged accelerator pump. The engine revs up slightly, then stumbles and pops loudly back through the carb before catching. But we never had that problem when starting out from idle. In our case, it's more like a progressive "bog" as you slowly advance the throttle once you are already on plane, and again, RPMs do not change at all. The change in the sound of the engine is subtle, but noticeable.

Hopefully we'll have some time next week to work on it again. I feel very comfortable that it's a simple fix. (Even rebuilding the whole carb is pretty easy compared to what we've been through over the past 2 months!) With any luck, it will be back to 100% by the second week in July. I'll post again once we've done some more sleuthing. And thanks again to everyone who has offered advice throughout this process! :)

Adam
 
Buffo, Can I ask how many hours and dollars you have invested so far in this rebuild. I had almost the exact thing happen to me on launch day this year (1st week of April). Based on my work schedule and access to a shop to work on the engine decided to go with a brand new crate motor and was back in the water in 3 weeks. I would have loved the experience of doing this myself but my life situation at the time wouldn't allow it. For pure curiousity sake I am just wanting to know the time and money involved in doing this yourself. You can PM or email me the info if you don't want to post it here, keithjab123 at yahoo dot com.
 
You must log in or register to reply here.
Back
Top